Illuminants



United States Patent ILLUMINANTS Jean A. M. Brock, St. Louis, Mo.,assignor to Olin Mathieson Chemical Corporation, East Alton, 111., acorporation of Virginia No Drawing. Filed July 15, 1958, Ser. No.749,577

3 Claims. (CI. 52-24) This invention relates to flare compositions, andparticularly to improved magnesium illuminant compositions.

The value of illuminating or flare compositions is gen erallyproportional to the candle power developed and the duration of theillumination. Thus, the candle power seconds generated by the combustionof such compositions is a reliable comparative measure of their value.The rapid oxidization of metallic magnesium is generally accompanied byan exceedingly brilliant light. Therefore, the most widely acceptedilluminants are based on mixtures of metallic magnesium and an oxidizingagent to which a binder may be added. It is a well-known expedient toincrease the luminosity of such compositions by reducing the particlesize of the magnesium, but this is attended by a reduction in theburning time. Thus, little or no significant increase in the candlepower seconds output of the compositions is obtained. Various otherattempts have been made to increase the brilliance of such compositionsbut in each instance the increased luminosity was accompanied by acorrespondingly increased burning rate and, in many instances, an actualdecrease rather than an improvement in the candle power seconds output.

It is, therefore, an object of this invention to increase the luminosityof flare compositions. It is also an object of this invention to providenovel and improved magnesium illuminating compositions. A more specificobject of this invention is to increase the candle power seconds outputof magnesium-oxidizing agent composi' tions.

The present invention, by which these and other objects are attained, ispredicated on the adidtion of small amounts of magnesium oxide (MgO) tomagnesiumoxidizer illuminating compositions. The particular manner inwhich the magnesium oxide acts is not fully understood but it has beenfound that the addition of mag nesium oxide within predetermined limitsto illuminating compositions based on metallic magnesium and aninorganic oxidizing agent increases the candle power of the mixturesupon combustion without having a deleterious effect upon the burningtime. Compositions containing between about 1% and about 5% magnesiumoxide provide this increased luminosity while optimum results areobtained whensuch compositions contain approximately 2.8% magnesiumoxide. Magnesium oxide in amounts less than about 1% by weight of thecompositions has no noticeable eifect on their burning characteristics;whereas when the magnesium oxide content is increased above about 5%,this compound acts as a diluent and actually detracts from theilluminating characteristics of the original composition.

The metallic magnesium is in finely divided form and to provide amixture with suitable burning characteristics must be of a particle sizesufliciently small to pass through a ZS-mesh screen. The burning rate ofthe composition can be controlled at least to some extent by controllingthe size of the metallic magnesium particles. Thus, the burning rate ofthe mixture is increased when magnesium having a smaller averageparticle size is utilized. Although magnesium particles beingsufficiently small to pass through a 40-mesh screen may be satisfactoryin some instances, when maximum luminosity is required it is preferredto use finely divided metallic magnesium that will pass through aZOO-mesh screen. Generally, the metallic magnesium content of thecompositions is maintained between about 40%and about 60%. Compositionscontaining less than about 40% metallic magnesium are quite diflicult toignite and upon combustion provide a flame having definitely inferiorilluminating qualities. As the metallic magnesium content is in creased,the ease of ignition, burning rate, and developed candle power alsoincrease. However, when-the amount of metallic magnesium in thecompositions exceeds approximately 60%, the compositions have a veryrapid burning rate and are susceptible to detonation. Thus, the metallicmagnesium content of the compositions must be maintained between about40% and 60%.

The compositions must also contain sufiicient oxidizing agent to insurethe complete oxidation of the metallic magnesium and the combustion ofthe plastic binder without forming excessive amounts of carbon. Thus,the oxidizer must be present in suflicient quantities to providesubstantially oxygen balanced compositions. Because of safety, economy,and ease of handling, sodium nitrate has been found most suitable foruse as an oxidizer in magnesium illuminant compositions and is thepreferred oxidizing agent in accordance with the present invention.However, other inorganic oxidizing agents such as barium nitrate,potassium nitrate, ammonium perchlorate, potassium perchlorate, and thelike can also be used in the formulations of the present invention.

Thilluminants of this invention are made in cohesive form and arepreferably compacted in cases. Polyvinyl acetate is the preferredbinder, but any other flammable plastic materials which are combustiblein this environment, which can be readily dissolved, and which will notproduce substantial ash or black smoke on combustion, can be used.Suitable binders include polyester resins, epoxy resins, phenolicresins, and the like. The binder is normally present in the compositionin ranges between about 4% and about 10% based on the weight of theentire mixture. Cohesive illuminants cannot be insured when smalleramounts of binder are used and larger amounts require inordinantproportions of the oxidizing agent to insure their complete combustion.

While the constituents making up the illuminants of the presentinvention can be mixed in any conventional manner, it is preferred toadd the metallic magnesium to a solution of the binder to form a uniformslurry and then add a premixture of the oxidizing agent and themagnesium oxide to this slurry. When a uniform mixture is obtained, thecomposition is shaped into any desired configuration and then hardenedby removal of the solvent. Although other sequences of incorporation ofthe ingredients can be employed, the preliminary mixing of the metallicmagnesium particles in the solution of the binder provides the metallicmagnesium with a protective coating before the addition of the othermaterials. Thus, the metallic magnesium is protected from atmosphericand oxidizing influences, and any danger of a premature re actionbetween the magnesium and the oxidizing agent is effectively inhibited.

In order to illustrate the present invention and its advantages,magnesium illuminants containing magnesium oxide were formulated andcompared with substantially identical compositions not containingmagnesium oxide. In each instance, the magnesium oxide and sodiumnitrate were thoroughly mixed in a ball mill for about a half hour toprovide a substantially homogeneous premixture. Meanwhile, a solution ofpolyvinylacetate was prepared by dissolving the polyvinyl acetate in twoparts of methylene chloride for each part of the binder. When thepolyvinyl acetate was completely dissolved, the metallic magnesium wasadded to the solution and uniformly dispersed therethrough by means of asigma blade mixer. After a substantially uniform dispersion of the magnesium was attained, the magnesium oxide-sodium nitrate premixture wasadded. Mixing was then continued for about 30 minutes until asubstantially uniform mixture was obtained. The resultant compositionwhich was virtually solvent-free was then formed into pellets about oneinch in diameter and having substantially the same length and weighingabout 25 grams. The residual methylene chloride was removed from thepellets by evaporation. The pellets thus obtained were ignited todetermine their luminosity and burning rates.

The results of these tests are set forth in the following table in whichluminosity is expressed in candlepower, burning time in seconds, andtotal output in candlepower seconds as cp.s. In these formulations andthroughout the specification and claims, all components are expressed inparts by weight.

Composition Composition Output Mix Mg NaNO; IVac MgO Lumi- Burning Cp.s.

nosity Time 10 The metallic magnesium in the first three mixes wassutfieiently fine to pass through a 200 mesh screen while the magnesiumused in mixes 4 and 5 had a considerably larger average particle sizebut was sufficiently small to pass through a 40-mesh screen. Bycomparing the luminosity and candlepower seconds of mixes 2 and 4, itwill be noted that although the luminosity of mix No. 2 is three timesas great as that of mix No. 4 due to the utilization of a smallerparticle size metallic magnesium that the candlepower second output ofthese two mixtures is substantially the same.

Mix No. 1 constitutes a preferred embodiment of the present invention.Basically this mixture has the same composition as mix No. 2 but differstherefrom in that magnesium oxide was added thereto at the expense ofthe polyvinyl acetate binder. By the inclusion of mag nesium oxide intothe composition, the candlepower was increased from 300,000 to 760,000while the burning time was only relatively slightly decreased from 3.60seconds to 2.24 seconds. This results in an increase in candlepowerseconds from 1.08 to 170x10 i.e., an increase of almost 60%.

Mix No. 5 represents another preferred embodiment of the inventionutilizing 40 mesh magnesium rather than the -200 mesh magnesium of mixNo. 1. Here again, the preferred embodiment represents a modification ofthe basic formulation of mix No. 4 by the addition of magnesium oxidethereto at the expense of the polyvinyl acetate. The addition of themagnesium oxide in this instance resulted in a four-fold increase ofcandlepower and a slight reduction in the burning time from 9.3 secondsto 8 seconds. Also, the candle power second output of mix No. 5 is morethan two and a half times greater than that of mix No. 4 not containingmagnesium oxide.

Mix No. 3, containing 14% magnesium oxide, is not within the scope ofthis invention. This example was included to show that excessive amountsof magnesium oxide have a deleterious effect upon magnesium illuminants. This is readily illustrated by this example in which theluminosity was decreased from 300,000 to about 131,000 cp. and thecandle power seconds output was reduced from 1.08 to 064x10 While theabove embodiments, particular formulations were given and theseformulations contained sodium nitrate and polyvinyl acetate, it will bereadily appreciated that various modifications can be made in theseformulations and also that other inorganic oxidizing agents and binderscan be utilized without departing from the scope of the presentinvention.

From the foregoing description, those skilled in the art should readilyunderstand that the invention accomplishes its objects and provides asubstantially improved magnesium illuminant. While one completedisclosure of the invention has been set forth in detail andmodifications indicated, it is not to be understood that the inventionis limited to such details of the disclosure but that such modificationsand variations thereof as do not depart from the spirit of the inventionare contemplated by and within the scope ofthe appended claims.

Having thus described the invention, what is claimed and desired to besecured by Letters Patent is:

1. An improved, substantially oxygen balanced illuminant consistingessentially of between about and about 60% magnesium, between about 1%and about 5% magnesium oxide, from between about 4 percent and about 10percent polyvinyl acetate and the balance sodium nitrate.

2. An improved substantially oxygen balanced illuminant consistingessentially of about magnesium, about 2.8% magnesium oxide, about 42.7%sodium nitrate and about 4.5% polyvinyl acetate.

3. An improved oxygen balanced illuminant consisting essentially ofbetween about 40% and about magnesium, between about 1% and about 5%magnesium oxide, between about 4% and about 10% of a flammable plasticbinder selected from the group consisting of polyvinyl acetate,polyester resins, epoxy resins and phenolic resins, and the balance aninorganic oxidizing agent selected from the group consisting of bariumnitrate, sodium nitrate, potassium nitrate, ammonium perchlorate andpotassium perchlorate.

3. AN IMPROVED OXYGEN BALANCED ILLUMINANT CONSISTING ESSENTIALLY OFBETWEEN ABOUT 40% AND ABOUT 60% MAGNESIUM, BETWEEN ABOUT 1% AND ABOUT 5%MAGNESIUM OXIDE, BETWEEN ABOUT 4% AND ABOUT 10% OF A FLAMMABLE PLASTICBINDER SELECTED FROM THE GROUP CONSISTING OF POLYVINYL ACETATE,POLYESTER RESINS, EPOXY RESINS AND PHENOLIC RESINS, AND THE BALANCE ANINORGANIC OXIDIZING AGENT SELECTED FROM THE GROUP CONSISTING OF BARIUMNITRATE, SODIUM NITRATE, POTASSIUM NITRATE, AMMONIUM PERCHLORATE ANDPOTASSIUM PERCHLORATE.